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Re: Scott Nixon power supplies

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  • jim@fmtunerinfo.com
    Hi Dennis, All good stuff and you know I ve learned that and much more from you, John, Walter and others over the last 17 years. And thanks for sharing your
    Message 1 of 5 , Dec 2, 2004
      Hi Dennis, All good stuff and you know I've learned that and much
      more from you, John, Walter and others over the last 17 years. And
      thanks for sharing your knowledge with us all. I did forget to
      mention the IEC socket. The IEC socket and an EMI/RFI network. I also
      didn't say I installed a current limiter and John's snubber circuit.
      As said I never worried about leaving it on but so many guys kept
      worrying even though I told them it would be OK. Many guys will only
      be happy when you tell them what they REALLY want to here! :-) Of
      course my "alternatives" can and will be left almost always on but
      has the benefit of filtering the AC from the wall a bit more. By the
      way, the single 6DJ8 doesn't supply gain but is used as a cathode
      follower only. I've listened to a SS Nixon and the tube+ version and
      prefer the tube+ version. More harmonic richness in the midrange. The
      great thing about the SN DACs is the price. I love the sound better
      than ANY DAC I've owned, borrowed or whatever. I know someone with a
      high dollar Audio Note 3.1? It's also a zero sampling DAC. Hopefully
      I can A/B them soon. No matter the outcome, I'll stick with the $475
      version Nixon and NIX the $$$$ Audio Note. 8:-) jim...
      --- In dallasaudioclub@yahoogroups.com, "Dennis Boyle"
      <chimeraone@w...> wrote:
      > With regards to operating tubes, RCA operated all their studio
      equipment
      > in the so-called "Stand-By" mode. The filaments were always on and
      the
      > B+ was switched on for operation. Tremaine's Audiocyclopedia
      references
      > this and tests proved the tubes operated longer and over time became
      > quieter. This was also standard on radio transmitters that used
      directly
      > heated power tubes.
      >
      > Cycling tube filaments and heaters, on and off, does significantly
      > reduce tube life. When cold the materials used to construct
      filament and
      > heaters has very low resistance. Due to the current surge on turn-
      on,
      > over 50 amps on a 211, the heater/filament material is mechanically
      > stressed and will eventually fail.
      >
      > A much worse condition is called "Thermal Stripping". This occurs
      when a
      > B+ is applied to a "cold" tube before the filament has reached
      operating
      > temperature. In this case the cathode or filament material that
      emits
      > free electrons is stripped away and the tube degrades fairly
      rapidly.
      > Might be the reason why so many modern tube amplifier manufacturers
      only
      > warrantee their tubes for 90 days. There are very few modern amp
      designs
      > that use separate filament and B+ power supplies. Since filament
      > transformers are cheap and readily available, DIY builders don't
      have to
      > answer to the accountants on keeping costs down.
      >
      > The simplest solution is a separate filament transformer that
      allows you
      > to either leave the filaments on all the time or to turn on the
      filament
      > supply on first. In this case you can put a readily available and
      cheap
      > Thermistor or Current Limiter on the primary (120VAC line) leads.
      You
      > can use these devices with an RC network in the B+ Supply for soft
      > start, although a 5AR4/GZ35, 5V4 or 6CA4 or any other Soft Start
      > rectifier diode is perhaps a better choice. The 5AR4 is a good
      choice
      > because it has very low dynamic output impedance which helps
      transient
      > performance and current production units sound good and are cheap.
      >
      > If you are going to use a filament winding on the B+ supply for the
      > rectifier tube, make sure the is at or slightly below the tube's
      rated
      > filament voltage. Use Ohm's Law to determine the correct value for a
      > couple resistors or even better some Thermistors/Current Limiters to
      > prevent current surge.
      >
      > These types of power supplies should extend the life and
      performance of
      > your tubes for a very long time. If you are operating the tubes at
      80%
      > or less of maximum ratings (voltage and current), they should last
      well
      > over 5 years, in the case of power tubes, and voltage amplifier
      tubes
      > may outlive you.
      >
      > Dennis
      >
      > -----Original Message-----
      > From: jim@f... [mailto:jim@f...]
      > Sent: Thursday, December 02, 2004 7:57 AM
      > To: dallasaudioclub@yahoogroups.com
      > Subject: [dallasaudioclub] Scott Nixon power supplies
      >
      >
      > Quite a few folks who own Scott Nixon DACs, locally and around the
      > web, have asked me if I worry about them always being on. I never
      did
      > but decided on a solution anway. The current home page photo show
      two
      > I've rebuilt. My two original SN Dacs now have these modified power
      > transformer sections. The new trannies I bought at Tanners. I've
      > added line filtering, an on/off switch in the rear and an "on" LED.
      > Pics of both below. One in a aluminum box and one in wood cigar
      box.
      > jim..
      >
    • Dennis Boyle
      Jim, As you might remember, my ears don’t like the 6DJ8/6922/ECC88 tubes. They have an edge that I think it due to their distortion ratios…too much higher
      Message 2 of 5 , Dec 2, 2004

        Jim,

         

        As you might remember, my ears don’t like the 6DJ8/6922/ECC88 tubes. They have an edge that I think it due to their distortion ratios…too much higher odd order harmonic distortion. I am sure this is minimized in a cathode follower application. It might be interesting to try some vintage E88CC European types just to see if they make a difference. They sound much more musical.

         

        The best tube buffer stage I ever heard was 71A DHT in a cathode follower configuration or better yet after it was modified to use   output transformers with the tube operating at a gain of 1. This was the tail end of a line preamp that use a 6J5 for the amp stage.

        Built by a Doctor in New Orleans who was nice enough to come up and let me listen to both versions after I sold him the output transformers to replace the ones he was using. They were some single ended transformers made by James, that cost very little and sounded pretty good. They are made in Taiwan and are sold on e-bay.

         

        Dennis Boyle

        Chimera Laboratories

        Website: http://www.chimeralabs.com/

        Website: http://home.att.net/~chimeraone/index.html

         

         

        -----Original Message-----
        From: jim@... [mailto:jim@...]
        Sent: Thursday, December 02, 2004 11:43 AM
        To: dallasaudioclub@yahoogroups.com
        Subject: [dallasaudioclub] Re: Scott Nixon power supplies

         


        Hi Dennis, All good stuff and you know I've learned that and much
        more from you, John, Walter and others over the last 17 years. And
        thanks for sharing your knowledge with us all. I did forget to
        mention the IEC socket. The IEC socket and an EMI/RFI network. I also
        didn't say I installed a current limiter and John's snubber circuit.
        As said I never worried about leaving it on but so many guys kept
        worrying even though I told them it would be OK. Many guys will only
        be happy when you tell them what they REALLY want to here! :-) Of
        course my "alternatives" can and will be left almost always on but
        has the benefit of filtering the AC from the wall a bit more. By the
        way, the single 6DJ8 doesn't supply gain but is used as a cathode
        follower only. I've listened to a SS Nixon and the tube+ version and
        prefer the tube+ version. More harmonic richness in the midrange. The
        great thing about the SN DACs is the price. I love the sound better
        than ANY DAC I've owned, borrowed or whatever. I know someone with a
        high dollar Audio Note 3.1? It's also a zero sampling DAC. Hopefully
        I can A/B them soon. No matter the outcome, I'll stick with the $475
        version Nixon and NIX the $$$$ Audio Note. 8:-) jim...
        --- In dallasaudioclub@yahoogroups.com, "Dennis Boyle"
        <chimeraone@w...> wrote:
        > With regards to operating tubes, RCA operated all their studio
        equipment
        > in the so-called "Stand-By" mode. The filaments were always on and
        the
        > B+ was switched on for operation. Tremaine's Audiocyclopedia
        references
        > this and tests proved the tubes operated longer and over time became
        > quieter. This was also standard on radio transmitters that used
        directly
        > heated power tubes.

        > Cycling tube filaments and heaters, on and off, does significantly
        > reduce tube life. When cold the materials used to construct
        filament and
        > heaters has very low resistance. Due to the current surge on turn-
        on,
        > over 50 amps on a 211, the heater/filament material is mechanically
        > stressed and will eventually fail.

        > A much worse condition is called "Thermal Stripping". This occurs
        when a
        > B+ is applied to a "cold" tube before the filament has reached
        operating
        > temperature. In this case the cathode or filament material that
        emits
        > free electrons is stripped away and the tube degrades fairly
        rapidly.
        > Might be the reason why so many modern tube amplifier manufacturers
        only
        > warrantee their tubes for 90 days. There are very few modern amp
        designs
        > that use separate filament and B+ power supplies. Since filament
        > transformers are cheap and readily available, DIY builders don't
        have to
        > answer to the accountants on keeping costs down. 

        > The simplest solution is a separate filament transformer that
        allows you
        > to either leave the filaments on all the time or to turn on the
        filament
        > supply on first. In this case you can put a readily available and
        cheap
        > Thermistor or Current Limiter on the primary (120VAC line) leads.
        You
        > can use these devices with an RC network in the B+ Supply for soft
        > start, although a 5AR4/GZ35, 5V4 or 6CA4 or any other Soft Start
        > rectifier diode is perhaps a better choice. The 5AR4 is a good
        choice
        > because it has very low dynamic output impedance which helps
        transient
        > performance and current production units sound good and are cheap.

        > If you are going to use a filament winding on the B+ supply for the
        > rectifier tube, make sure the is at or slightly below the tube's
        rated
        > filament voltage. Use Ohm's Law to determine the correct value for a
        > couple resistors or even better some Thermistors/Current Limiters to
        > prevent current surge.  

        > These types of power supplies should extend the life and
        performance of
        > your tubes for a very long time. If you are operating the tubes at
        80%
        > or less of maximum ratings (voltage and current), they should last
        well
        > over 5 years, in the case of power tubes, and voltage amplifier
        tubes
        > may outlive you.           

        > Dennis

        > -----Original Message-----
        > From: jim@f... [mailto:jim@f...]
        > Sent: Thursday, December 02, 2004 7:57 AM
        > To: dallasaudioclub@yahoogroups.com
        > Subject: [dallasaudioclub] Scott Nixon power supplies

        >
        > Quite a few folks who own Scott Nixon DACs, locally and around the
        > web, have asked me if I worry about them always being on. I never
        did
        > but decided on a solution anway. The current home page photo show
        two
        > I've rebuilt. My two original SN Dacs now have these modified power
        > transformer sections. The new trannies I bought at Tanners. I've
        > added line filtering, an on/off switch in the rear and an "on" LED.
        > Pics of both below. One in a aluminum box and one in wood cigar
        box.
        > jim..
        >







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      • jim@fmtunerinfo.com
        Hello Dennis, You may know that I ve always agreed with you on the 6DJ8 issue. I even talked with Scott about that before I bought my first DAC. It doesn t
        Message 3 of 5 , Dec 7, 2004
          Hello Dennis, You may know that I've always agreed with you on the
          6DJ8 issue. I even talked with Scott about that before I bought my
          first DAC. It doesn't seem to be an issue as the cathode follower in
          the Nixon's application. I've "rolled" a few tubes and have been
          happiest with a Mullard. I picked up a Telefunken this weekend and
          plan on trying it. Maybe some day I'll build a different audio stage
          but I'm as happy as can be for now. I really enjoy music through this
          DAC. I'm using a one meter pair of the interconnect you loaned me
          between the Nixon DAC and my preamp. That was a nice improvement. You
          won't be getting those back! Sorry. 8:-) I didn't figure there would
          have been an improvement but there was. I was already using Vampire
          Wire. But of course your winding, materials and RCAs are all
          different. jim...
          --- In dallasaudioclub@yahoogroups.com, "Dennis Boyle"
          <chimeraone@w...> wrote:
          > Jim,
          >
          > As you might remember, my ears don't like the 6DJ8/6922/ECC88 tubes.
          > They have an edge that I think it due to their distortion ratios…too
          > much higher odd order harmonic distortion. I am sure this is
          minimized
          > in a cathode follower application. It might be interesting to try
          some
          > vintage E88CC European types just to see if they make a difference.
          They
          > sound much more musical.
          >
          > The best tube buffer stage I ever heard was 71A DHT in a cathode
          > follower configuration or better yet after it was modified to use
          > output transformers with the tube operating at a gain of 1. This
          was the
          > tail end of a line preamp that use a 6J5 for the amp stage.
          > Built by a Doctor in New Orleans who was nice enough to come up and
          let
          > me listen to both versions after I sold him the output transformers
          to
          > replace the ones he was using. They were some single ended
          transformers
          > made by James, that cost very little and sounded pretty good. They
          are
          > made in Taiwan and are sold on e-bay.
          >
          > Dennis Boyle
          > Chimera Laboratories
          > Website: HYPERLINK
          > "http://www.chimeralabs.com/"http://www.chimeralabs.com/
          > Website: HYPERLINK
          > "http://home.att.net/~chimeraone/index.html"http://home.att.net/~chi
          mera
          > one/index.html
          >
          >
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